Synthetic smoking material

ABSTRACT

THE INVENTION IS CONCERNED WITH A METHOD OF PRODUCING AN OXIDIZED POLYSACCHARIDE FOR USE IN A SYNTHETIC SMOKING MATERIAL, WHEREIN THE POLYSACCHARIDE IS TREATED IN AN OXIDIZING SYSTEM CONTAINING AT LEAST STOICHIOMETRIC QUANTITIES OF NOTROSONIUM ION FOR URONIC OZIDATION

March 13, 1973 r J.- H'. ARENDT ETAL 3, 0,

I SYNTHETIC SMOKiNG MATERIAL Filed Aug. 30, 1971 v US. Cl. 260212 8 Claims ABSTRACT OF THE DISCLOSURE The invention is concerned with a method of producing an oxidized polysaccharide for use in a synthetic smoking material, wherein the polysaccharide is treated in an oxidizing system containing at least stoichiometric quantities of nitrosonium ion for uronic oxidation.

A synthetic smoking material which can be smoked like tobacco, but which is readily reproducible with consistant properties, and which has a simple smoke chemistry, has long been desired.

It has recently been proposed to make a synthetic smoking material from an oxidized cellulose, produced by an oxidizing reaction using liquid nitrogen dioxide. The oxidized cellulose produced in this way has certain disadvantages as a synthetic smoking material, particularly the tendency for its physical properties to change on ageing. For example, it tends to darken in colour and to gel, probably as a result of hydrolysis, into a rigid form which is difiicult to shred and handle on conventional tobacco handling machinery. Believing these ageing characteristics to be related to the manner in which the cellulose is oxidized, our research has been directed to other oxidizing agents for the cellulose and we now find that an apparently better oxidizing system is one using the NO+ (Nitrosonium) ion, in at least stoichiometric quantities. It also appears that a suitable raw material for incorporating in a synthetic smoking material can be produced not only from the oxidation of cellulose but also from the oxidation of other polysaccharides.

In accordance therefore with the present invention we produce an oxidized polysaccharide for use in a synthetic smoking material by treating the polysaccharide in an oxidizing system containing at least stoichiometric quantities of nitrosonium ion for uronic oxidation.

This method results in predominantly uronic oxidation with little ring oxidation, a low degree of degradation of the polysaccharide molecule, and a low degree of cross linking, that is lactone formation, between chains or within individual chains. The oxidation proceeds at a very high reaction rate and produces an oxidation of 95% (expressed as oxidation of anhydro-glucose units to anhydro-glucuronic acid units according to the calcium acetate method of analysis) in 6 hours or even less. The process is much easier and less dangerous than other oxidation systems, particularly liquid nitrogen dioxide systems. The oxidized product exhibits little or no adverse ageing characteristics and requires no subsequent reduction step, owing to the absence of ring carbonyls. The properties of the oxidized material give a good smokeability, and good mechanical strength and flexibility so that it can readily be handled by conventional tobacco handling machinery.

The nitrosonium ion in the oxidation system may be provided by a combination of a strong acid and a nitrosonium ion releasing constituent such as a nitrite, any tetranitrato metal complex, nitrosyl sulphate, and nitrosyl nited States Patent ICC chloride. Examples of nitrites which can be used include the alkali or alkali earth metal nitrites, particularly sodium nitrite owing to its cheapness. Examples of the strong acids which can be used are: inorganic acids such as phosphoric acid (not less than sulphuric acid (not less than 65%), and strong organic acids such as trifluoroacetic acid, trichloroacetic acid in acetic acid, benzene sulphonic acid, anthranilic acid, para-aminobenzoic acid these solid acids being dissolved in acetic acid.

Acetic acid itself cannot be used alone because of its weak acidity. As far as inorganic acids are used, phosphoric acid is recommended owing to its dehydrating power which favours the formation of N0+ from the equilibrium H NO NO++H Q its low degrading effect on cellulose and polysaccharides compared to HNO or HCl, and its weak reactivity with polysaccharides (the P content of the oxidized material obtained is below 0.01%).

If the acid is too strong, hydrolysis and chain degradation may occur. To counteract these difiiculties solvents or diluents can be added to the acid concerned to reduce these etfects.

The solvents or diluents must be passive, that is they must not react permanently with the acid, with the nitrosonium ion, with the polysaccharide, or the oxidized polysaccharide. Examples of suitable solvents or diluents are water, dioxane, ethyl acetate, dimethyl formamide, dimethyl sulphoxide, and cyclohexane, or mixtures of these.

Alternatively instead of reacting a nitrosonium ion releasing constituent with a strong acid, to produce the nitrosonium ions in the oxidizing system, nitrosonium salts may be used dissolved in a pure polar organic solvent. The polar organic solvent should be free of any groups which can induce its nitrosation, such as hydroxyl amino, keto groups or activated aromatic rings, and may be for example nitromethane, nitrobenzene, dimethyl sulphoxide, or mixtures of such solvents. The reaction temperature can be between 0 C. and 50 C. but a temperature in the region of 20 C. is believed to be preferable. The pressure should be between 0 and 20 atmospheres, prefferably 1 atmosphere. The atmosphere over the reaction mixture can be made of pure oxygen or pure nitric oxide but is preferably simply air.

The polysaccharide to be oxidized may be a cellulosic material, such as cotton linters, regenerated cellulose, paper cellulose, or highly purified wood pulp, or it may be a polysaccharide such as starch or dextran, or another polysaccharide with hexopyranose rings free of groups containing nitrogen or sulphur. It has been found that some interesting materials could be obtained by using the oxidizing process of the invention with dialdehydrocellulose containing up to 20% of the theory of aldehydic groups in the chain, dicarboxycellulose (up to 20% of carboxyl) trialcohol cellulose (up to 20% of primary alcohol on the ring) ruthenium tetroxide oxycellulose, and all cellulose or polysaccharides pre-oxidized by various means, as long as their oxidation degree is not too high, preferably below 20% of the theory, and insofar as they do not contain troublesome impurities.

Although the materials obtained by this process burn well by themselves, it has been found that the incorporation of mineral salts in the fibres improved the smoking taste of the material, lowering the irritancy, and giving an improved ash-formation. Among the salts used, phosphates, citrates, and oxalates are preferred, such as calcium or magnesium phosphate, calcium or magnesium citrate and calcium or magnesium oxalate the content of these salts in the material can range from 5% by weight up to 30%. These salts are introduced in the fibres by means of the ion-exchange technique. The oxidized material is treated with aqueous solutions of calcium or magnesium acetate or formate, the cations being thus exchanged with the carboxyl groups of the oxidized material, the acetic or formic acid formed being eliminated by washing with water. Then the material is treated with an aqueous solution of ortho-phosphoric, citric or oxalic acid which precipitates the corresponding salt within the fibres. However crystals of the salts are also formed on the surface of the material and this is unfavourable to the colouration of the material when after production it is impregnated with tobacco extracts, to produce a synthetic smoking product in its final form.

Thus, after the mineralization, the material is treated with dilute aqueous acidic solution for a very short period, and washed carefully with water. After this treatment the material absorbed tobacco extracts quite well from their aqueous solution and after drying its appearance was acceptable. By this technique the removal of the mineralizing agent was mainly localized on the surface of the fibres, and the salt content remained between 5-10% by weight. In addition, this led to the improvement of the smoking properties.

In the case where tobacco flavourings added to the product are very sensitive to attack by micro-organisms, it has been found that sorbic acid (as potassium sorbate) or butanediol-1,3 added to the flavourings in the proportion of 0.2% by weight of synthetic product avoided the development of fungi, without alfecting the smoke taste.

The following examples illustrate the invention and the relevant large scale laboratory apparatus is illustrated in the accompanying drawing.

EXAMPLE 1 155 g. of cellulose in sheet form was impregnated with sodium nitrite by rapid soaking of the sheet into a saturated aqueous solution of sodium nitrite at room temperature followed by 10 seconds of hanging-out and then drying at room temperature until the moisture content was 8%. This process led in every case to a sodium nitrite content ranging between 1.5101 g. per g. of cellulose, and can be made in a continuous run.

The air dried impregnated product (473 g.) was then cut into strands and introduced into a 20 litre reaction flask A connected to a separating funnel B from one side and to a flask C (containing an aqueous solution of sodium hydroxide) fitted with a condenser D, through the trap E, in the other side. 9 litres of 85% H PO were then displaced from the container F to B by applying vacuum. The acid was then introduced into A by opening of the tap H, and the suspension homogenized with the mechanical stirrer G.

The NO and N gases evolved are eliminated in the following manner. NO is converted into N0 by means of a current of air through the system, and the whole N0 is converted into sodium nitrite and nitrate by reaction with the sodium hydroxide solution of flask C.

The reaction is stopped by diluting the phosphoric acid with water, after a period depending on the required oxidation degree. After 70 minutes, an oxidation degree of 60% was obtained (carboxyl and lactone groups content included), after 80 minutes an oxidation degree of 75% and for higher oxidation levels (95%) 5 hours of reaction were required.

Following dilution, the liquid phase was decanted and the oxidized product which was still in form of strands was removed from the flask, thoroughly washed on a funnel and soaked in water to complete the removal of any remaining H PO In this way 120 gr. of carboxycellulose were obtained with a nitrogen content between 0.4 and 0.8% by weight. This material was then mineralized by the ion-exchange technique, treated with the weak acid solution and then impregnated with tobacco extracts to give a product whose aspect is similar to natural tobacco, and which when made into cigarettes, had acceptable smoking properties,

The process could be adapted to full commercial production by suitable upscaling of the apparatus.

EXAMPLE 2 As in Example 1, except that H PO is replaced by a mixture of H PO 40% aqueous dioxane in the respective proportion of 9 to 1 by volume. Under these conditions six hours are necessary to obtain an oxidized cellulose with a carboxyl content of 62% and the oxidized fibrous material has improved flexibility.

EXAMPLE 3 As in Example 1, except that the strands are not impregnated with sodium nitrite, nitrosyl sulphate being added to the suspension, in the proportion of 4 g. per gram of cellulose to be oxidized. The mixture is stirred for 10 hours and the degree of oxidation obtained is 70%. In this case also, addition of dioxane to the phosphoric acid (90% H PO 40% aqueous dioxane in the proportion 9:1 by volume) improved the flexibility of the material.

EXAMPLE 4 As in Example 3, but with tetranitratozincate (2NO+, Zn(NO replacing nitrosyl sulphate in the proportion of 6 g. per gram of cellulose to be oxidized. In this case 6 hours are necessary to obtain a degree of oxidation of 65%.

EXAMPLE 5 As in Example 1, except that 85% H PO is replaced by a mixture of CF COOH/dioXane in the ratio 10:1 by volume and in the proportion of 40 ml. per gram of pure cellulose. The cellulose must be impregnated with NaNO or NaNO must be added to the suspension with stirring. To reach an oxidation degree of 60% by this method, the sodium nitrite proportion to be used is 7 g. per gram of cellulose, and the reaction time must go from 15 to 20 hours. Careful washing with hot methanol and water has to be carried out until all the fluorine has been removed.

EXAMPLE 6 l0 grams of cellulose dried for 6 hours over P 0 at C., are suspended in 1000 ml. of nitromethane containing 98.1 g. of dissolved tetranitratozincate. The suspension is left for six days at 15 C., and then the liquid phase decanted. The cellulose is then washed on a funnel, first with pure nitromethane, then with ethanol and finally with water. The material thus obtained has a degree of oxidation of 65% and has very good physical properties.

We claim:

1. A method of producing an oxidized polysaccharide for use in a synthetic smoking material, wherein the polysaccharide is treated in an oxidizing system containing at least stoichiometric quantities of nitrosonium ion for uronic oxidation, said nitrosonium ion being provided by a combination of a nitrosonium ion releasing constituent and a strong acid selected from the group consisting of phosphoric acid, sulphuric acid, trifiuoroacetic acid, trichloroacetic acid, benzene sulphonic acid and paraaminobenzoic acid.

2. A method according to claim 1 in which said nitrosonium ion releasing constituent is selected from the group consisting of a nitrite, a tetranitrato metal complex, nitrosyl sulphate, and nitrosyl chloride.

3. A method according to claim 1, wherein said strong acid is phosphoric acid and said nitrosonium ion releasing constituent is a nitrite.

4. A method according to claim 1, wherein said oxidation system includes a passive diluent to reduce hydrolysis and chain degradation resulting from the presence of the strong acid.

5. A method according to claim 4, wherein said passive diluent is one or more of water, dioxane, ethyl acetate, dimethyl formamide, dimethyl sulphoxide, or cyclohexane.

6. A method according to claim 1, wherein said oxidation is carried out at a reaction temperature of between 0 C. and 50 C. and at a pressure of between 0 to 20 atmospheres.

7. A method of producing an oxidized polysaccharide for use in a synthetic smoking material, wherein the polysaccaride is treated in an oxidizing system containing at least stoichiometric quantities of nitrosonium ion for uronic oxidation, the nitrosonium ion in said oxidation system being-provided by a nitrosonium salt dissolved in a pure polar organic solvent.

8. A method according to claim 7, wherein said polar organic solvent is one or a mixture of more than one of nitromethane, nitrobenzene, or dimethyl sulphoxide.

References Cited UNITED STATES PATENTS 2,730,524 1/1956 Nieuwenhuis 260-212 5 2,472,590 6/ 1949 Kenyon et al. 260-233.3 R 2,557,473 6/1951 Ryan 260--233.3 R 3,516,416 6/ 1970 Briskin et a1 260212 DONALD E. CZAJA, Primary Examiner 10 R. W. GRIFFIN, Assistant Examiner US. Cl. X.R.

131-2; 260-209 R, 209 D, 233.3 R 

